Activation of  -diacylglycerol kinase is critical for the mitogenic properties of anaplastic lymphoma kinase

Abstract

IntroductionThe anaplastic lymphoma kinase (ALK) gene, localized on chromosome 2p23, encodes for a large, glycosylated 200-kDa membranespanning tyrosine kinase receptor whose expression is highly tissue specific, being restricted to components of the nervous system; structural homology studies place ALK within the family of insulin receptor tyrosine kinases (RTKs), with the highest homology to the leukocyte tyrosine kinase (LTK). 1,2 Involvement of ALK in the pathogenesis of hematopoietic malignancies derives from the observation that constitutively active forms of ALK are detected with a high frequency in anaplastic large-cell lymphomas (ALCLs), a subgroup of non-Hodgkin lymphomas, predominantly of T or null type. 3 The oncogenic forms of ALK are the result of somatic chromosome translocations that fuse the ALK cytoplasmic domain to the 5Ј region from different partner genes. The most frequent oncogenic version of ALK is represented by nucleophosmin (NPM)/ALK, an 80-kDa hybrid protein created by the t(2;5)(p23; q35) rearrangement. 4,5 The tumorigenic properties of NPM/ALK have been demonstrated in vitro in different cell systems [6][7][8][9] and confirmed in vivo by the generation of NPM/ALK-mediated tumor models. [10][11][12][13] Despite several studies, the pathogenic mechanisms leading to ALK-mediated transformation remain still poorly defined.Thus far, several signaling molecules have been identified that associate and/or are activated by ALK, including growth factor receptor-bound protein 2 (Grb2), Src homology and collagen (Shc), insulin receptor substrate-1 (IRS-1), phospholipase C-␥ (PLC-␥), p60 src , and phosphatidylinositol 3-kinase (PI3-K), although only a few have been shown to be strictly specific for ALK's transforming potential. 3 In particular, several lines of investigation have indicated that both PLC-␥ and PI3-K are critical transducers of NPM/ALK-mediated oncogenesis through activation of mitogenic and/or survival signals, 8,[14][15] while the exact role of the ras/mitogen activated protein kinase (MAPK) cascade needs further evaluation. 3 The contribution of p60 src has been recently evaluated in NPM/ALK-positive cell lines and demonstrated through the effects of p60 src down-regulation and pharmacologic inhibition on cellular proliferative rate. 16 Additional relevant effectors of NPM/ALK-mediated lymphomagenesis are represented by signal transducer and activator of transcription 3 (Stat3) and Stat5. 17 Obviously, further investigations are needed to identify other pathways that are operative in ALK-positive malignancies and that could represent intracellular targets for a more appropriated therapeutic intervention in ALCL treatment. For personal use only. on May 11, 2018. by guest www.bloodjournal.org From Diacylglycerol kinase (DGK) has attracted much attention in recent years since growing evidence indicates its direct involvement in the regulation of signal transduction processes. The family of mammalian DGKs comprises 9 isoenzymes classified in 5 distinct groups on the basis of their ...

Diacylglycerol kinase-α phosphorylation by Src on Y335 is required for activation, membrane recruitment and Hgf-induced cell motility

“…Furthermore, either pervanadate treatment of endothelial cells or constitutive activation of Lck in T cells result in tyrosine phosphorylation and activation of Dgk-a (Cutrupi et al, 2000;Cipres et al, 2003). Despite these data strongly suggest that Dgk-a is regulated by tyrosine phosphorylation, no tyrosine phosphorylation of Dgk-a had been detected upon stimulation with either HGF, VEGF, IL-2 or upon activation of the ALK receptor in different cell types (Cutrupi et al, 2000;Cipres et al, 2003;Baldanzi et al, 2004;Bacchiocchi et al, 2005).…”

“…Activation and membrane recruitment of Dgk-a G Baldanzi et al et al, 2003;Baldanzi et al, 2004;Bacchiocchi et al, 2005).…”

“…Conversely, we previously showed that inhibition of Dgk-a activity, obtained either pharmacologically or by expression of dominant-negative mutant or by RNA interference, impairs HGF-, VEGF-and anaplastic lymphoma kinase (ALK)-induced chemotaxis and proliferation in several cell types (Cutrupi et al, 2000;Baldanzi et al, 2004;Bacchiocchi et al, 2005), as well as in vitro angiogenesis in endothelial cells (Baldanzi et al, 2004). Similarly in T cells, pharmacological inhibition of Dgk-a severely impairs IL-2-induced G1-S phase transition (Flores et al, 1999).…”

“…Activation of Dgk-a by tyrosine-kinase receptor and IL-2, requires Src-family tyrosine kinase activity and involves association of Dgk-a with either Src or Lck (Cutrupi et al, 2000;Cipres et al, 2003;Baldanzi et al, 2004;Bacchiocchi et al, 2005). Furthermore, either pervanadate treatment of endothelial cells or constitutive activation of Lck in T cells result in tyrosine phosphorylation and activation of Dgk-a (Cutrupi et al, 2000;Cipres et al, 2003).…”

Diacylglycerol kinase α mediates HGF-induced Rac activation and membrane ruffling by regulating atypical PKC and RhoGDI

“…We previously showed that DGKα is activated by growth factors on recruitment to the plasma membrane through its Src-mediated phosphorylation on Tyr 335 . Activation of DGKα mediates growth-factor-induced cell migration and proliferation in epithelial, endothelial, and lymphoma cells (8)(9)(10)(11)(12). Moreover, we demonstrated that in epithelial cells, DGKα is required for hepatocyte growth factor (HGF) -induced membrane ruffling by regulating Rac membrane targeting and activation (13).…”